In general, spiral ducts are widely used in air handling units, pipelines for transferring particles and so on.
An apparatus for manufacturing a spiral duct has a plurality of pressing rollers arranged in a plurality of lines. While a thin metal plate member wound around a reel stand passes through the pressing rollers, both ends of the metal plate member are bent away from each other. Then, as the metal plate member is pressed by the pressing rollers while the bent portions of both ends of the metal plate member are coupled to each other, the metal plate member is formed into a cylinder. At this time, as the metal plate member is guided while being supported by three to five projecting guide rods installed along the circumferential direction of the cylinder, a cylindrical spiral duct is formed. When the spiral duct is formed to have a proper length, it is cut by a circular cutter.
In the process of manufacturing the spiral duct, the pressing rollers for bending both ends of the metal plate member, and the pressing rollers for pressing both ends of the metal plate member, are driven by a plurality of gears or chains.
Such a representative spiral duct manufacturing apparatus is disclosed in Korean Unexamined Utility Model No. 1999-5329 (hereinafter, referred to as “related art 1”). Referring to FIGS. 1A to 1E, the construction of the spiral duct manufacturing apparatus will be described.
As shown in FIGS. 1A to 1E, the spiral duct manufacturing apparatus according to the related art carries a metal plate member 18, supplied from a reel stand 19, through a plurality of bending rollers 21 arranged in a plurality of lines so as to bend both ends of the metal plate member 18. Then, both ends of the metal plate member 18 are pressed by pressing rollers 31 so as to form a cylindrical duct, and the duct is cut by a circular saw blade 42. At the exit side of the bending rollers 21, a transfer unit 2 including a pair of driving rollers 22 is installed on a first table 11. The driving rollers 22 are composed of a lower driving roller 24 which is connected to a cylinder 25 so as to operate in the vertical direction, and an upper driving roller 23 which is disposed above the lower driving roller 24 and receives power from a driving motor 26.
On a second table 12, a forming unit 3 is installed, including a bolt 32 which adjusts a pressing force for coupling the bent portions 18a and 18b of the metal plate member 18 supplied from the transfer unit 2, a pair of pressing rollers 31 to which the distal end of a lever 33 having the bolt 32 fastened thereto is coupled, and a circular frame 34 which guides a duct which is formed in a cylinder shape while passing through the pressing rollers 31.
The circular frame 34 has a spiral guide groove 35 formed on the inner circumferential surface thereof, the spiral guide groove 35 serving to guide the duct.
Under the forming unit 3, a cutting unit 4 is installed on the second table 12.
The cutting unit 4 includes an operating plate 41 which slides on the second table 12, a bracket 46 which is installed on the distal end of the operating plate 41 so as to connect the circular saw blade 42, a motor 43 for rotating the circular saw blade 42, and a cylinder 44 which adjusts the height of the circular saw blade 42.
On the second table 12, a cylinder 47 for moving and returning the cutting unit 4 is installed. The first and second tables 11 and 12 are connected through a guide plate 5.
The spiral duct manufacturing apparatus according to the related art winds a metal band, supplied at an oblique angle, into a cylindrical shape, thereby manufacturing a spiral duct.
The spiral duct manufacturing apparatus can manufacture a spiral duct formed in a straight line, but cannot manufacture a spiral duct having an elbow which is bent at a predetermined angle depending on a place where the spiral duct is installed.
Further, a spiral duct manufacturing apparatus and method is disclosed in Korean Patent Laid-open Publication No. 2006-28859 (hereinafter, referred to “related art 2”) filed by the present applicant. FIGS. 2 A and 2B show the spiral duct manufacturing apparatus.
As shown in FIGS. 2 A and 2B, the spiral duct manufacturing apparatus according to related art 2 includes a first edge forming roll 10 for forming a double folded portion 31 on both edges of a metal band 30, a cutting roll 20 whose horizontal rotation angle periodically varies so as to cut the metal band 30 supplied from the first edge forming roll 10 into a wave or straight line shape along the longitudinal direction, and a seaming device 50 which winds the cut metal band 30 into a spiral shape while coupling a single folded portion 32 to a double folded portion 31.
The spiral duct manufacturing apparatus can manufacture not only a straight spiral duct but also a spiral duct having an elbow. Since the elbow is formed in such a manner that the outer circumference thereof is set in a straight line, the elbow is not formed in a gently curved line, but in a straight line which is bent several times at various angles.